The invention relates generally to lightwave communication systems and, more particularly, to secure transmission of information in dense wavelength division multiplexing systems.
Optical fiber has become the transmission medium of choice for communication networks because of the speed and bandwidth advantages associated with optical transmission. Wavelength division multiplexing (WDM), which combines many optical signals at different wavelengths for transmission in a single optical fiber, is being used to meet the increasing demands for more speed and bandwidth in optical transmission applications. With recent advances in optical networking technology, system manufacturers are now contemplating dense wavelength division multiplexing (DWDM) systems that carry, for example, as many as 40, 80, or more channels in a single fiber.
With the increased capacity provided by these DWDM systems, data security becomes a major concern because of the increased amount of transmitted information that is susceptible to being unlawfully accessed. In most public networks, end users implement data security measures such as encryption before supplying information for transmission. One of the more common encryption techniques is to use cryptographic codes to scramble or alter the content of the data. Unfortunately, even some of the most sophisticated codes have been compromised by so-called xe2x80x9chackersxe2x80x9d using advanced technologies.
In general, DWDM systems do not incorporate data security measures. Moreover, if information is scrambled at all, it is typically done for reasons other than security. Using Synchronous Optical Network (SONET) systems as an example, information transmitted within an optical channel is scrambled to ensure that the transmitted information is less susceptible to the adverse effects of optical impairments. For example, scrambling is used to avoid the occurrence of a consecutive string of xe2x80x9c0xe2x80x9ds or xe2x80x9c1xe2x80x9ds in a data stream, the disadvantages of which are well known to those skilled in the art. However, the scrambling patterns and techniques used in SONET transport are not meant to be xe2x80x9csecretxe2x80x9d codes and, as such, are not considered as a data security measure for safeguarding the content of the transmitted information.
The security of information transmitted in a DWDM system is substantially improved according to the principles of the invention with a transmission scheme that incorporates multiple stages of scrambling with a unique multiplexing arrangement. More specifically, information supplied by one or more sources is multiplexed according to a predetermined scrambling pattern and transmitted in a parallel format using one or more wavelength channels in a wavelength division multiplexed signal. By transmitting the multiplexed and scrambled information in parallel, the wavelength channels effectively function as a parallel bus (a xe2x80x9cwavelength busxe2x80x9d).
Data security is further augmented according to the principles of the invention using a hierarchical approach in which multiple stages of scrambling can be applied to the multiplexed and scrambled information transported in the wavelength bus. For example, individual bit streams carried within each wavelength channel of the wavelength bus can be separately scrambled according to another predetermined scrambling pattern. Individual bit streams can also be routed among the wavelength channels according to another predetermined scrambling pattern so that the order of the wavelength channels is effectively scrambled. Information can also be transferred among multiple wavelength buses to provide yet another level of scrambling.
Consequently, the wavelength bus provides a very flexible transport architecture that is particularly well-suited for incorporating data security measures to augment user-provided encryption and the like. Additionally, the wavelength bus offers many transmission-related efficiencies as compared to prior DWDM transport schemes. Some examples include, but are not limited to, more efficient bandwidth utilization, reduced latency because of less serial-to-parallel and parallel-to-serial conversions, and resource sharing among a group of wavelength channels.